Making keto and aldo aliphatic carboxylic acids



Patented May 3, 1927.

ALFRED nuisance, or manna meannnm-oN-rnn-an c. n. noanamena scan,cnnmscnr. FABBIK, or nnmn, (manna, a socnrrx or caaxnw.

m. GEBIANY, ASBIGNOB 'ro NmnEn-mcnLnnm-oN-Tnnmaxim} xn'ro AND ALDOamrnn'r'rccannoxrmc ACIDS.

No Drawing. Application filed December 22, 1825, Serial No. 77

This invention relates to a method of making aldo and keto aliphaticcarbox llc acids or their salts and consists in dehy ro-- boxylic acidsobtained by the de ydrogena tion into the aldo or keto aliphaticcarboxylic acids or their salts.

In carryin out'this process, the hydroxyaliphatic car oxylic-acidsserving as starting material, e. g. lactic acid, glycolic acid,u-hydroxybutyric-acid, malic acid, tartaric acid and the like may, forexample, first be converted into the esters corresponding to .the saidacids. These esters are dehydrogenated in the vapor hase by oxygen whichmay advantageously e added for example in the form of oxygengas-mixtures, containing air, oxygen or ozone, or which may be suppliedby substances yielding ox.'gen, e. g. heated metallic oxides, over whicthe vaporized esters are passed In the deh drogenating process thealcohol group of t e hydroxy compounds is converted into the carbonylgroup, thereby making esters of aldo or keto aliphatic carbox lie-acids,from which the corresponding a1 0 or keto aliphatic carboxylic-acids areobtained by a further treatment, for example by saponification. Theprocess will be advantageously carried out in the presence of suchvapours which do not disturb the reaction, e. g. steam, by the aid ofwhich the temperature may be regulated and the rate ofreactioncontrolled thereby avoiding violent or explosion-like reaction.

The process, particularly the dehydrogenatiiig with oxygen, may bepreferably carried out in the presence of contact substances. Suchcontact substances are, 0 gen compounds derived from metals capabe ofvarious degrees of 0x dation. Particularly eifective are oxides 0 anacid character in the free form, or combined as salts. Good results areobtained when using the'following kind of catalysts: vanadium pentoxide,molybdenum trioxide, uranium oxide, the

vanadates, uranates, molybdates of copper and silver, lead chromate,nickel chromate and so on.

,094, and in Germany larch 5, 1923.

Furthermoreferric oxide, nickel and co.- bal t made, the. oxides ofmanganese, copper oxide, the oxides of the rare earths and others mayalso be employed as catalysts.

In some cases it has to make use of several catalysts, for example ofmlxtures of various catalysts. The catalysts can be activated by theaddition of certain substances having no catalytic ualitles themselves.They should preferab y be employed upon porous carrying substances,such. as pumice stone, unglazed china, asbestos and the like, but alsoon metals with rough surfaces, e. g. aluminium, iron, copper and so on.

The reaction is taking place even at ordinary temperature or attemperatures below 100 C. But preferably the process should 7 be carriedon at raised temperatures, for example between 100 and 500 0. Excellentyields are ,generally obtained when working between 200 and 400 C. Forinstance, when using the lactic acid'esters of the aliphatic alcohols asstarting material, it was found that temperatures of about 200-350 C.yielded particularly ood resalts. The process may be carrie out atordinary or increased pressure, or as well in a vacuum. In general, itis advisable to proved advantageous adapt the pressure to the stabilityof the esters employed, in such a way that unstable esters are treatedat lower pressures, more stable esters at higher pressures.

Examples.

. 1. Glycolic acid methyl ester in the va or phase with twice to tentimes the theoretical amount of oxygen required is passed through aniron or copper tube at 220-350 at an atmospheric or a slightly increasedpressure, by which process glyoxylic methyl ester is o tained with ayield of 50-60% of. the theory, in mixture with unconverted glycolicacid ester. The obtained product is saponified according to the ordinarymethods and, if necessary, separated from unchanged glycolic acid bysteam distillation.

cm-on on 2 doocnf 2 toocn, 2. 200 grams of lactic acid ethyl ester inthe va or phase are passed at 300 to 400 over a out 1000grams ofvanadium pentoxide spreadon a carrier, e. g. asbestos. Ap-

roximately 160 grams of d1stillate containmg 55 to 70% yroracemlc acidethyl ester VllCllll Ill.

3. 100 grams of lactic acid ethyl ester or methyl ester in the vaporphase are mixed with an excess of air and passed through a tube heatedat 250 to 300 and charged with vanadium pentoxide on asbestos ascarrying substance. By condensing the vapors produced 90 to 100 grams ofcondensate are obtained, which contains to pyroracen ic acid ethyl esteror methyl ester respectively. This condensate 1s saare obtained;-

ponified with water above atmospheric pressure, and from the aqueoussolution -pyroracemic acid with a yield of 7 ii-853% of the theory isproduced by evaporation in the After the sa onification of thepyroracemic acid ester tie aqueous solution may as well be neutralizedwith alkall metal hydroxide, alkali metal carbonate or bicarbonate, orwith earth alkali metal carbonates,

and evaporated, whereupon the pyrovinates will be obtained in a pureform by separating them from lactates that may b crystallization or byprecipitation from t e aqueous solution with alcohol.

CH] CHI 2 dnon+o,--.z do rzmo 4. a-oxy-butyric acid is esterified withethyl alcohol according to the usual methods;

then the ester is 'dehydrogenated' in the vapor phase at temperaturesbetween 300 an 350 C. and a pressure of mm.

mercury with ozonized air and trioxide of molybdenum or vanadate ofcopper as catalyst. In the produced condensate of the vapors there are60 to 70% a keto butyric acid ethyl ester, which may be converted intothe. free'acid or into salts of the latter in the ordinary manner.

cm 7 cm l+ :+HaO

oocim doocm.

It is advisable, but not essential, to rovide for the presence ofsubstances com ining with water for the purpose of avoiding losses dueto by-reactions, which may be caused by the .water formed in the courseof the reaction, e1 g. by saponification of the esters and destructionof the free acid. It was, however, found that even in the absence becarried lhrou quite successfully, without any' consi erable disturbancebeing caused by the saponification. From the aldo or keto aliphatic.carboxyhc-acid esters thus obtainedthe free aldo or keto aliphaticcarboxylic-acids or their salts can be produced accordin to the ordinarymethods, the free acid, or example, by saponification with water underpressure or only by boiling with water under reflux and concentration ofthe aqueous solution. Further the salts of the aldo or keto aliphaticcarboxylic acids may be rodured from the acids in accordance witi thewell-known methods of salt production, f. e. neutralization of the freealdo of such precautions the process can generally or. keto aliphaticcarboxylic-acids 'with bases or carbonates or by conversion with saltsof weak acids. Besides, the salts of the aldo' or keto aliphaticcarboxylic-acids may be obtained directlyfrom their esters, e. g.'b'ycarefully sapomfying the esters with alkali metal hydroxide, alkalimetal carbonate or bicarbonate, or with earth-alkali-metal hydroxide orearth-alkali-metal carbonate and water, by evaporationor byprecipitation of thesalt from the aqueous solutionwith suitable meanssuch as alcohol and so on. p

In the same manner, or in a similar way, also other aldo or keto alihatic carboxylicacids maybe produced, or instance oxalacetic acidfrommalic acid, phenyl glyoxyl ic acid from phenyl glycohc acid, phenylpyroracemic acid from phenyl lactic acid, or from the esters of theoxy-acids in question.

coca

CO OR can can b11011 00 0003 doOld on. can 6H1 Moreover, purely alihatic aldo or keto aliphatic carboxylic-aci s, as glyo lic acid orpyroracemic acid, can be pro need in a,-

similar manner also b way of such esters of glycolic acid or of lacticacid as are derived from alcohols being others than those mentionedabove, as for example from butyl alllcolipil, isoamyl alcohol, benvzylalcohol and t e i e.

Whenever, in the present application, mention is made of compounds,these are meant to refer to the general formula iJOOR' with the provisothat B may be hydrogen or a hydrocarbon radical. R may be hydrogen ormetal. For example for pyroracemic acid and for the salts of this acidthe formula is the following:

Claims:

1. The method of making keto and aldo aliphatic carboxylic acids whichcomprises dehydrogenating esters of hydroxy aliphatic carboxylic acidsin the vapor phase by the action of oxygen and converting the obtainedesters into the respective acids.

2. The method of making keto and aldo aliphatic carboxylic acids whichcomprises dehydrogenating esters of hydroxy aliphatic carboxylic acidsin the vapor phase by the action of gas mixtures containing free oxygenand converting the obtained esters into the correspondinn acids.

3. The method of making keto and aldo aliphatic carboxylic acids whichcomprises dehydrogcnating esters of hydroxy aliphatic carboxyllc acidsin the vapor phase by the action of gas mixtures containing free oxygenand ozone and converting the obtained esters into the correspondingacids.

4. The method of making keto and aldo ali hatic carboxylic acids whichcomprises de ydrogenating esters of hydroxy ali hatic carboxylic acidsin the vapor hase y the action of oxygen in presence water vapor andconverting the obtained esters into the corresponding acids.

- 5. The method of making keto and aldo aliphatic carboxylic acids whichcomprises dehydrogenating esters of hydroxy aliphatic carboxylic acidsin the vapor phase by the action of gas mixtures containing free oxygenin presence of water vapor and. converting thed obtained esters into thecorresponding aci s.

6. The method of making keto and aldo aliphatic carboxylic acids whichcomprises dehydrogenating esters of hydroxy aliphatic carboxylic acidsin the vapor phase by the action of oxygen in presence ofoxygen-containing compounds of metals capable of various degrees ofoxydation and converting thedsobtained esters into the corresponding aci7. The method of making keto and aldo aliphatic carboxylic acids whichcomprises dehydrogenating esters of hydroxy aliphatic carboxylic acidsin the vapor phase by the action of oxygen in presence of acidic oxidesof metals capable of various degrees of oxydation and converting theobtained esters into the corresponding acids.

8. The method of making keto and aldo aliphatic carboxvlic acids whichcomprises dehydrogenating esters of hydroxy aliphatic carboxylic acidsin the vapor phase by the action of oxygen at tem eratures ofapproximatel 100500 C. an converting the obtaine esters into thecorresponding acids.

9. The method of making pyroracemic acid which comprises dehydrogenatinglactic acid esters in the vapor phase by the action of oxygen andconverting the obtained esters into pyroracemic acid.

10. The method of making pyroracemic acid which comprisesdehydrogenating the esters of lactic acid with aliphatic alcohols in thevapor phase by the action of oxygen at temperatures between 200350 C.and converting the obtained pyroracemic acid ester into pyroracemicacid.

In testimony whereof I aflix my signature.

ALFRED HKUSSLER.

